The present invention relates to duplicating equipment and more particularly to a hand-held dual roller device for applying pressure to a pressure sensitive duplicating master and a method of duplication using the device. In order to produce copies from this type of duplicating master, the master and a sheet of copy paper are placed on a hard surface with the side of the duplicating master bearing the printing ink next to the copy paper. The duplicating master and copy paper are pressed together to transfer the image from the master to the face of the copy paper.
It is known in the art to apply the pressure required for duplication to a master by means of a roller device. U.S. Pat. No. 555,653, issued Mar. 3, 1896, to Millert, shows a hand-held roller device having two metallic rollers journalled in the ends of pivotally mounted bars. The pivoting arrangement is said to permit the roller device to follow the contour of a book in which a copy is to be imprinted. It is significant that both rollers in this device are metal and apparently function in the same manner.
Other roller devices, having dual rollers, are shown in U.S. Pat. No. 274,549, issued Mar. 23, 1883 to Baldwin; and U.S. Pat. No. 2,610,580, issued Sept. 16, 1952 to Burke. Both the Burke and Baldwin devices have dual roller arrangements in which it is contemplated that the rollers will not be used simultaneously. Both devices have one roller which is used to apply water or other solvent prior to copying. The second roller is used subsequently to apply pressure during the copying process.
U.S. Pat. No. 3,090,301, issued Mar. 21, 1963 to Arounowa, shows a device for manually transferring a pattern which is marked in dye on a pattern roller. A second roller is used to supply solvent to either the pattern roller or to the surface on which the pattern is to be printed such that pattern transfer will be made. In one embodiment of the Arounowa device, the solvent roller is used to apply solvent to the surface to be imprinted just ahead of the transfer roller. There is no suggestion in this reference, however, of using the device for pressure sensitive duplicating.
It is desirable when using a pressure sensitive duplicating master to apply uniform pressure over the entire master since image transfer is dependent solely upon pressure applied to the master. If a hard rubber or metal roller is used to apply pressure to the pressure sensitive duplicating master and the copy paper, irregularities in the surface upon which the master and copy paper rest may result in voids in the duplicated image. Such voids may also occur if the roller is irregularly shaped. Thus, it is seen, there is a need for a means for applying pressure to a pressure sensitive duplicating master and copy paper which will result in clear copies being produced, regardless of slight irregularities in the surface upon which the duplicating master and copy paper rest.